Sensors for monitoring at least one of pressure and temperature, sometimes interchangeably called transducers, have been used successfully in the downhole environment of oil and gas wells for several decades, and are still conventional means for determining downhole pressures, such as, for example, bottom-hole pressure and annulus pressure. For example, quartz pressure sensors may be used to determine downhole pressure. Conventionally, an isolation element and an isolation fluid are disposed between a working environment that is being monitored for temperature and pressure changes and the sensor of the transducer used to conduct the measurements. Isolation elements may, for example, include diaphragm structures, bladder structures, and bellows structures. In addition, a variety of fluids have been employed as isolation fluids including various hydrocarbon liquids.
Sensor isolation schemes should protect the sensor from the fluid environment being measured and enable accurate, responsive, and repeatable measurements by the sensor when in use. Furthermore, the isolation element and its connection to the sensor or housing in which the sensor is located should be substantially immune to any hostile properties of the fluid environment. Non-limiting areas of potential application for such an isolation element include downhole applications (e.g., drilling applications, exploration applications, production applications, completion applications, logging applications, etc.), aerospace applications, purified liquid and gas handling applications, medical applications, petrochemical applications, and other industrial applications.
Many materials that may be present in a working environment in which a sensor is placed should be substantially isolated from the sensor. Examples of such materials include hydrogen, hydrogen sulfide, carbon dioxide, oxygen, water, and various solvents, some of which may readily permeate components of a conventional isolation element and/or may chemically degrade (e.g., deteriorate, corrode, etc.) the components. Material diffusion through the isolation element can interfere with desired movement (e.g., expansion, compression, etc.) of the isolation element, can reduce measurement accuracy and/or precision, and can even render the isolation element inoperative. For example, diffused hydrogen (e.g., diffusion hydrogen gas, diffused hydrogen ions, etc.) may undesirably deform components (e.g., diaphragm structures, bladder structures, bellows structures, etc.) of the isolation element, which may result in undesirable calibration shifts, zero offsets, and/or component damage (e.g., rupture). In addition, the components of the isolation element, particularly those of thin wall cross-section, can deteriorate over time when exposed to highly corrosive fluids (e.g., liquids, gases, combinations thereof, etc.). Furthermore, elevated temperatures and/or elevated pressures, such as those present in downhole applications, can accelerate undesirable material diffusion and/or chemical degradation.
It would, therefore, be desirable to have new methods, structures, and assemblies that mitigate one or more of the problems conventionally associated with sensor isolation.